// This optional code is used to register a service worker.
// register() is not called by default.

// This lets the app load faster on subsequent visits in production, and gives
// it offline capabilities. However, it also means that developers (and users)
// will only see deployed updates on subsequent visits to a page, after all the
// existing tabs open on the page have been closed, since previously cached
// resources are updated in the background.

// To learn more about the benefits of this model and instructions on how to
// opt-in, read https://bit.ly/CRA-PWA

const isLocalhost = Boolean(
    window.location.hostname === "localhost" ||
        // [::1] is the IPv6 localhost address.
        window.location.hostname === "[::1]" ||
        // 127.0.0.0/8 are considered localhost for IPv4.
        window.location.hostname.match(
            /^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/
        )
)

export function register(config) {
    if (process.env.NODE_ENV === "production" && "serviceWorker" in navigator) {
        // The URL constructor is available in all browsers that support SW.
        const publicUrl = new URL(process.env.PUBLIC_URL, window.location.href)
        if (publicUrl.origin !== window.location.origin) {
            // Our service worker won't work if PUBLIC_URL is on a different origin
            // from what our page is served on. This might happen if a CDN is used to
            // serve assets; see https://github.com/facebook/create-react-app/issues/2374
            return
        }

        window.addEventListener("load", () => {
            const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`

            if (isLocalhost) {
                // This is running on localhost. Let's check if a service worker still exists or not.
                checkValidServiceWorker(swUrl, config)

                // Add some additional logging to localhost, pointing developers to the
                // service worker/PWA documentation.
                navigator.serviceWorker.ready.then(() => {
                    console.log(
                        "This web app is being served cache-first by a service " +
                            "worker. To learn more, visit https://bit.ly/CRA-PWA"
                    )
                })
            } else {
                // Is not localhost. Just register service worker
                registerValidSW(swUrl, config)
            }
        })
    }
}

function registerValidSW(swUrl, config) {
    navigator.serviceWorker
        .register(swUrl)
        .then(registration => {
            registration.onupdatefound = () => {
                const installingWorker = registration.installing
                if (installingWorker == null) {
                    return
                }
                installingWorker.onstatechange = () => {
                    if (installingWorker.state === "installed") {
                        if (navigator.serviceWorker.controller) {
                            // At this point, the updated precached content has been fetched,
                            // but the previous service worker will still serve the older
                            // content until all client tabs are closed.
                            console.log(
                                "New content is available and will be used when all " +
                                    "tabs for this page are closed. See https://bit.ly/CRA-PWA."
                            )

                            // Execute callback
                            if (config && config.onUpdate) {
                                config.onUpdate(registration)
                            }
                        } else {
                            // At this point, everything has been precached.
                            // It's the perfect time to display a
                            // "Content is cached for offline use." message.
                            console.log("Content is cached for offline use.")

                            // Execute callback
                            if (config && config.onSuccess) {
                                config.onSuccess(registration)
                            }
                        }
                    }
                }
            }
        })
        .catch(error => {
            console.error("Error during service worker registration:", error)
        })
}

function checkValidServiceWorker(swUrl, config) {
    // Check if the service worker can be found. If it can't reload the page.
    fetch(swUrl, {
        headers: { "Service-Worker": "script" },
    })
        .then(response => {
            // Ensure service worker exists, and that we really are getting a JS file.
            const contentType = response.headers.get("content-type")
            if (
                response.status === 404 ||
                (contentType != null && contentType.indexOf("javascript") === -1)
            ) {
                // No service worker found. Probably a different app. Reload the page.
                navigator.serviceWorker.ready.then(registration => {
                    registration.unregister().then(() => {
                        window.location.reload()
                    })
                })
            } else {
                // Service worker found. Proceed as normal.
                registerValidSW(swUrl, config)
            }
        })
        .catch(() => {
            console.log("No internet connection found. App is running in offline mode.")
        })
}

export function unregister() {
    if ("serviceWorker" in navigator) {
        navigator.serviceWorker.ready
            .then(registration => {
                registration.unregister()
            })
            .catch(error => {
                console.error(error.message)
            })
    }
}
